1. Field of the Invention
The present invention concerns a process for removing an aqueous slurry suspension comprising blast medium and coating substance residues.
2. Description of the Related Art
One process for removing an aqueous slurry suspension is known from WO 96/16770 A, in which a) the suspension is collected in a receiving tank by means of gravity; b) the feed capacity of the mixture is increased by diluting it with water; c) the diluted mixture is fed to a settling tank by means of a vacuum; d) the (solid) blast medium is separated from the water by sedimentation, and the water is recycled. In addition, this prior known teaching discloses large amounts of water mixed with the blast medium for the purpose of dilution for removal to a further receiving tank to which the mixture to be treated can be fed, if necessary by means of a vacuum from the collection tank, and from which the mixture is further fed to the settling tank.
In EP-A-1 004 398 on the other hand, an aqueous slurry suspension is concentrated under a vacuum in order to separate the suspension.
New processes for cleaning surfaces which have a corrosion protection coating on the surface utilize dripable fluids (e.g. water), in addition to the dry abrasives from sandblasting. In contrast to dry blasting, in which the abrasive-coating substance-rust mixture can be easily removed by vacuuming, in wet blasting a slurry of abrasive material, surface residues and liquid is created, with a volume proportion of 10%–40% solid material. A separation of solids and fluids occurs in practice due to gravity, such that a process is required which must be capable of removing from the work area a broad spectrum of residues with from less than 5% to more than 90% solids. This is made more difficult on ships, for example, where access to the work area is limited by manholes of about 600 mm diameter and the required feed height can be more than 30 meters.
The invention is therefore based on achieving a process for optimal suction capable of collecting and then feeding a broad spectrum of slurry materials with abrasive components distributed over a wide work area over height differentials of up to 30 meters and more.
The five-phase process according to the invention begins with the initial suction of the aqueous slurry suspension into a receiving tank in which a further dilution with water is required to achieve a feed capability of the diluted suspension which can then, by means of a pump, overcome a height differential of at least 5 meters. Then, according to the invention, the solid material is separated from the water by simple sedimentation, and the water is recycled.
The use of the inventive device on ships, where particular spatial limitations must be observed, is a further aspect of the invention. According to the invention a housing with a diameter <600 mm is advantageous for this purpose.